1. Field of the Invention
The present invention relates to a control system including an electronic control apparatus and a plurality of sensor devices each having a communication function and connected to the control system, the sensor device with a communication function, and the electronic control apparatus.
2. Description of Related Art
There are known drive apparatuses incorporating a sensor and an actuator. As such a drive apparatus, there is one incorporating a memory to store its characteristic values. For example refer to Japanese Paten Application Laid-open No. 2008-057413. Initial characteristic values are written into the memory of the drive apparatus at the time of shipment thereof, so that an electronic control unit (ECU) can control the drive apparatus based on the initial characteristic value.
Further, there is known a technique in which learned values acquired through control by an electronic control apparatus are written into a memory incorporated in a drive apparatus in order to prevent the learned values from being lost when the electronic control apparatus is repaired or replaced.
Incidentally, to adopt such a technique for such a drive apparatus incorporating a memory, it is necessary to provide the drive apparatus with a communication function enabling the electronic control apparatus to read initial characteristic values from the drive apparatus or write learned values into the drive apparatus. Generally, it is possible to communicably connect a plurality of drive apparatuses to an electronic control unit through respective separate communication lines, if the electronic control unit is provided with communication devices dedicated to the respective drive apparatuses. However, it is desirable to connect the plurality of the drive apparatuses to the electronic control apparatus through a common communication line used as a bus.
To adopt such a bus connection, it is necessary to assign the respective drive apparatuses with different node IDs, so that communication can be performed between the electronic control apparatus and each of the drive apparatuses using the node IDs. However, in this case, a problem may occur as described below. Let's consider an example in which injectors of the respective cylinders of an engine are connected as drive apparatuses to an electronic control apparatus. As is well known, fuel injection control is performed such that injection signals outputted from the electronic control apparatus are inputted to an electronic driver apparatus (EDU), and the electronic driver apparatus drives the injectors based on the injection signals. That is, the fuel injection control is performed independently of memory access from the electronic control apparatus to the injectors through the communication line.
Here, it is assumed that the injector assigned with a node ID of 2 is erroneously mounted on the first cylinder although it should be mounted on the second cylinder, and the injector assigned with a node ID of 1 is erroneously mounted on the second cylinder although it should be mounted on the first cylinder.
In this case, since the electronic control apparatus erroneously reads the characteristic values from the injector mounted on the second cylinder as the characteristic values of the injector of the first cylinder, fuel injection control cannot be performed correctly.
A similar problem may occur in a case where analog sensor signals (analog output signals of sensors) are inputted to a electronic control apparatus through respective signal lines (sensor output lines) provided for respective drive apparatuses without through a communication line as shown in FIG. 1. In this case, the connection relationship between the sensors respectively incorporated in the drive apparatuses and the electronic control apparatus is determined physically by the sensor output lines, however, the connection relationship between the memories respectively incorporated in the drive apparatuses and the electronic control unit is determined logically by the node IDs assigned to the drive apparatuses.
Accordingly, if the sensor of the drive apparatus assigned with the node ID of 2 is erroneously connected to a first sensor output line although it should be connected to a second sensor output line, and the sensor of the drive apparatus assigned with the node ID of 1 is erroneously connected to the second sensor output line although it should be connected to the first signal line, the electronic control apparatus erroneously compensates the sensor signal from the drive apparatus having the node ID of 2 received through the first sensor output line, in accordance with the characteristic values of the drive apparatus having the node ID of 1 received through the communication line.